SB 603 
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Copy 1 



r. S. DEPARTMENT OF AGRICULTURE, 

BUREAU OF ENTOMOLOGY— BULLETIN No. 111. 

L. O. HOWARD. Entomologist and Chief of Bureau. 



THE HOP APHIS IN THE 
PACIFIC REGION. 



WILLIAM B. PARKER, M. S. 

Entomological Assistant. 



Issued May 6, 1913. 




WASHINGTON: 

GOVERNMENT PRINTING OFFICE. 

1913. 



U. S. DEPARTMENT OF AGRICULTURE, 

BUREAU OF ENTOMOLOGY— BULLETIN No. 111. 

L. O. HOWARD, Entomologist and Chief of Bureau. 



THE HOP APHIS IN THE 
PACIFIC REGION. 



WILLIAM B. PARKER, M. S. 

Entomological Assistant. 



Issued May 6. 1913. 




WASHINGTON: 
GOVERNMENT PRINTING OFFICE. 

1913. 



v.* 



9S 



BUREAU OF ENTOMOLOGY. 

L. (). Howard, Entomologist and Chief of Bureau. 

C. L. Marlatt, Entomologist and Acting Chief in Absence of Chief. 

R. S. Clifton, Executive Assistant. 

W. F. Tastet, Chief Clerk. 

F. H. Chittenden, in charge of truck crop and stored -product insect investigations. 

A. D. Hopkins, in charge of forest insect investigations. 

W. D. Hunter, in charge of southern field crop insect investigations. 

F. M. Webster, in charge of'cereal and forage insect investigations. 

A. L. Quaintance, in charge of deciduous: fruit insect investigations. 

E. F. Phillips, in charge of bee culture. % 

D. M. Rogers, in charge of preventing spread of moths, field work. 

Rolla P. Currie, in charge of editorial work. 

Mabel Colcord, in charge of library. 

Truck Crop and Stored Product Insect Investigations. 

F. If. Chittenden ; in eliargc. 

C. H. Popenoe, Wm. B. Parker, H. 0. Marsh, M. M. High, John E. Craf, P'red 
A. Johnston, C. F. Stahl, U. E. Fink, A. B. Duckett, entomological assistants. 

I. J. Condit, R. S. Vaile. collaborators in California. 

W. N. Ord, collaborator in Oregon. 

Thos. H. Jones, collaborator in Porto Rico. 

Marion T. Van Horn, Pauline M.Johnson, Anita M. Ballinger, Cecilia Sisco, 
preparators. 



% CF D. 
MAY 17 1913 



LETTER OF TRANSMITTAL 



l . S. Department of Agriculture, 

Bureau of Entomology, 
Washington, D. C, December 21, 1912. 
Sir: I have the honor to transmit herewith the manuscript of a 
paper entitled "The hop aphis in the Pacific region," prepared with 
admirable thoroughness by Mr. William B. Parker, Entomological 
Assistant. The topic is one which has engaged Mr. Parker's atten- 
tion for two seasons, 1911 and 1912. The work covers investigation 
in the States of Washington, Oregon, and California. The principal 
work was conducted in California, but the author has had consider- 
able experience with hop insects, including the hop aphis, in British 
Columbia. The principal insect pests of the hop have not, until 
recent years, had adequate treatment in publications on economic 
entomology, and this paper should therefore prove of great value to 
hop growers. 

I recommend its publication as Bulletin No. Ill of this bureau. 
Respectfully, 

L. O. Howard, 
Entomologist and Chief of Bureau. 
lion. James Wilson, 

Secretary of Agricultun . 



CONTENTS 



Page. 

Introduction 9 

Economic importance 9 

Life history 10 

Hibernation 10 

Aphides on hop roots 10 

Emergence from hibernation 12 

Method of reproduction 12 

Number of generations on alternate host 13 

Migrating forms 13 

Migratory activities 13 

Deposition of young 14 

Rate of growth 15 

Number of young deposited by viviparous females 16 

The fall migrants 17 

The winter egg 17 

The life cycle 18 

Theory regarding summer migrants 18 

Habits 19 

Habitation 19 

Protection 19 

Relation of ants to the hop aphis 19 

First appearance of the hop aphis in the season 20 

Favorable and unfavorable conditions for the aphis 20 

Effect of heat 20 

Food plants 21 

Nature of damage 21 

General effect of aphides upon hops 21 

Honeydew and its effect on the hops 22 

Blackening of hops 22 

Natural enemies 22 

Control of the hop aphis 23 

Axioms of successful control 23 

Insecticides used 23 

Time to begin spraying 23 

Number of applications 24 

Necessity for early spraying 24 

Necessity for thorough work 24 

Procrastination 24 

Spraying experiments 24 

Mixing nicotine solutions and whale-oil soap 27 

Preparation of the flour paste 27 

Advantages of flour paste over whale-oil soap as a spreader for contact insec- 
ticides 28 

5 



6 THE HOP APHIS IN THE PACIFIC REGION. 

Control of the hop aphis — Continued. Page. 

Quassia 28 

Effect of spray materials upon the qnalit y of sprayed hops 30 

Direction in which to work 30 

Control on prune 31 

Field observations 31 

Spraying report 31 

Spraying machinery 31 

Boiling and mixing plant 32 

Field operations 32 

Supply wagon 33 

Exchange tanks 33 

Spray rods 33 

Nozzles 33 

The compressed-air Bpraying machine 33 

Cost of spraying 35 

Cultural methods 36 

Clean culture 36 

Stripping the vines 36 

Picking off infested leaves 37 

Fertilization and irrigation 37 

General summary, with recommendal ions 37 

The more important writings on the. hop aphis 38 

Index 41 



LLUSTRATIONS. 



PLATES. 

Page. 
Plate I. Fig. 1. — Nymphs and winged forms of the hep aphis (Phorodon hu- 

muli) on hup leaves. Fig. 2.- Winter eggs of the hop aphis 12 

II. Fig. 1. Wingless progeny of winged hop aphides from alternate 
host. Fig. 2. — Willows along edge of hopyard, which were erro- 
neously supposed to harbor hop aphides : 20 

III. Fig. 1. — Normal hop cones and hop cones injured by the hop aphis. 
Fig. 2. — Vines severely injured by the hop aphis, showing lack of 

growth as compared with uninjured vines 20 

1 V . Fig. 1. — Hopvines severely injured by the hop aphis, and left in the 

field. Fig. 2. — Enlarged view of damaged and moldy hopvines. . 20 
V. Fig. 1. — Eggs of Hippodamia convergens among hop aphides. Fig. 

2. — Syrphus fly larvae feeding upon the hop aphis 20 

VI. Fig. 1. — Hindu laborer cooking flour paste. Fig. 2. — Boiling and 

mixing plant used at Independence, Oreg 28 

VII. Fig. I . — Hand pump and barrel on sledge. Fig. 2. — Knapsack spray- 
ing machine in use in hopyard 32 

VIII. Fig. 1. — Power outfit on narrow truck, in use in hopyard. Fig. 2. — 

Filling power outfit from improvised supply wagon 32 

IN. Fig. I. Compressed -air spraying machine, showing air bottle, tank, 
reducing valve, and pressure gauge. Fig. 2. — Filling air bottles 

for ( •< >in ] >ressecl-air spraying machine 32 

X. Fig. 1. — Hopvine stripped, and tied below the point of stripping, 
showing free condition of all foliage. Fig. 2. — Hopvine stripped, 
and tied above the point of stripping, showing matted condition 
of lower foliage 3G 

TEXT FIGURES. 

FlQ. 1. Field cages so placed as to catch any hop aphides that might emerge 

from eggs deposited upon the hop roots 11 

2. The hop aphis (Phorodon humuli): Wingless viviparous female 13 

3. The hop aphis: Winged female migrant 14 

4. Head of the hop aphis, showing frontal tubercles 15 

."). Head of i he melon aphis I Aphis gossypii) 1"> 

(i. The hop aphis: Nymph, showing wing-pads 17 

7. Diagram showing relative number of aphides in different parts of a 

single hopyard, indicating the increased infestation near Santa Rosa 

< reek 20 

5. Short-pole hopyard, showing dense foliage around base of vines, which 

.harbors the hop aphis 3G 

7 



THE HOP APHIS IN THE PACIFIC REGION. 

(Phorodon liumulJ Schrank.) 



INTRODUCTION. 

The hop aphis (Phorodon humuli Schrank) was known as a pest in 
the hop gardens of England and of Continental Europe long before 
hop growing became an industry in America. In the United States 
this aphis first appeared in New York in 1863, in Michigan in 1866, 
and in Wisconsin in 1867, and in these States it seriously injured that 
crop during the early eighties. It soon reached the Pacific Coast, 
where it first appeared in 1890, and it is now troublesome in most of 
the hop-growing sections of British Columbia; Washington, Oregon, 
and California. 

The investigation upon which this paper is based began during the 
spring of 1911 and was continued through two seasons, being com- 
pleted in the fall of 1912. Experiments were conducted and practical 
control work was carried on at Sacramento and Santa Rosa, Cal., 
and at Independence, Oreg. The recorded efficiency of the various 
insecticides tested is based upon actual counts of living aphides, 
made before and after spraying. The data upon the cost of control 
work and methods employed in field operations are based upon the 
work at Santa Rosa, Cal., and Independence, Oreg., where the prime 
object of this investigation was carried out, i. e., the economical 
control of the aphis of the hop. 

Acknowledgments are due to Dr. F. H. Chittenden, in charge of 
Truck Crop and Stored Product Insect Investigations; to Mr. J. 
Williamson, of Santa Rosa, Cal., who generously assisted me in some 
of the experimental work; to Mr. Theo. Eder, superintendent of the 
E. Clemens Horst Co., who furnished me with a field laboratory and 
a temporary assistant during the summer; to Mr. R. S. Raven, who 
ably assisted me in the life-history and experimental work, and to 
Mr. II. N. Ord, who collected much of the data upon methods and 
cost of control and who carried out the field work in Oregon. 

ECONOMIC IMPORTANCE. 

The hop aphis has probably been present on the Pacific coast 
since the time hops have been growm there on a large scale. The 
greatest injuries from this pest occur in Oregon, Washington, and 
British Columbia, but serious losses are occasionally sustained in 
California. 

74956°— Bull. Ill— 13-— 2 9 



10 THE HOP APHIS IN THE PACIFIC REGION. 

In 1911 the hops at Santa Rosa, Cal., were severely attacked by 
this aphis. In fact, if the hop crop of the world had not been small 
and the demand for hops consequently very great, many of the 
growers in this section would have been unable to dispose of their 
crops. During the same season the financial loss due to injury by 
this aphis to the crops on two large yards in British Columbia was 
estimated at $80,000. 

In 1912 the Joss due to this insect was particularly severe in Ore- 
gon. One company which handles about 20,000 bales estimated 
that 50 per cent of their hops were badly damaged and would sell 
for 15 cents per pound, while 30 per cent was slightly damaged and 
would sell between 15 and 18 cents per pound. The remaining 20 
per cent was not injured and would sell for the prevailing price of 
20 cents. At this rate the loss would aggregate $124,000. The crop 
on a yard of 110 acres was so severely injured that 20 acres were not 
worth picking. The loss in this yard was $12,000. 

The damage in these cases was unusually severe, but this pest if 
not controlled is, under favorable conditions, capable of causing 
such injury to both the hopvines and the hop cones as to entail a 
total loss. 

LIFE HISTORY. 

HIBERNATION. 

The winter egg is deposited by the oviparous female upon the 
plum, prune, and hop in the Pacific Coast States and upon the sloe, 
plum, bullace, 1 and probably the hop in England and Continental 
Europe. 

The first generation and the winged migrants were observed upon 
French prune at Santa Rosa and Perkins, Cal., during May and 
June in 1911 and 1912. The migrants which were observed May L".), 
1912, were upon the ordinary though tender foliage, but those 
observed later in the season were found only upon some very succu- 
lent, suckerlike growths. No hop aphides were found upon the 
surrounding older and tougher leaves. This observation was made 
both in Santa Rosa and Perkins, and it was found that by selecting 
such growths aphides could almost invariably be found. 

APHIDES ON HOP HOOTS. 

Prof. W. T. Clarke, of the California Experiment Station, stated 
that while studying this insect at Watsonville, Cal., during the last 
of January or first of February, 1904, some hop roots were brought 
to him on which were many living hop aphides, lie stated that 
there is no doubt about the identification of this insect. The writer 

i Journ. Board Agr. Great Britain, vol. 19, No. 4, p. 297, 1912, 



LIFE HISTORY. 



11 



was unable to find this condition, but the foregoing data show the 
possibility of another method of hibernation. 

Many examinations of hop roots were made during this investiga- 
tion, but do eggs of the hop aphis were discovered on or near them. 
The following data, however, lead the writer to believe that the 
aphides very frequently hibernate on or around the hop roots. 

Wingless viviparous hop aphides were observed depositing young 
upon the lower leaves of a hopvine at Santa Rosa, Gal., March 16, 
1912. This vine was half a mile from any prune tree. Many small 
wingless aphides were observed on the lower leaves of hopvines at 



















j JB 




i\*i 


; fl 












BiS^^" 






■ 

''I 







Fig. 1.— Field cases so placed as to catch any hop aphides that might emerge from eggs deposited upon, 
the hop roots. 1 0riginal-) 

Perkins, May 16, 1912, No winged migrants were observed at this 
time. 

The iirst winged migrants were observed at Perkins on May 24, 
both on the prune and the hop, and in the latter case were only on 
the upper leaves, the lower leaves being entirely free. 

Although field cages (fig. 1) which were placed over hopvines in 
February and removed after the surrounding vines were thoroughly 
infested did not contain any hop aphides, the fact that aphides were 
present on the hops before the winged migrants appeared and that 
they were found upon the lower leaves, while the winged forms 



12 THE HOP APHIS IN THE PACIFIC REGION. 

collect on the uppermost leaves, seems evidence enough to establish 
the hop as a winter host of the hop aphis, at least in these localities. 

It lias been thought possible that the hop aphis may hibernate 
upon some plants other than the plum, prune, sloe, and hop, and 
during this investigation many observations were made upon plants 
in the vicinity of the hops, for the winter eggs. While observing the 
winged migrants at Independence, Oreg., they were discovered upon 
cherry, alder, peach, and apple, and were found depositing young 
upon these plants. 

In order to see if the young would mature on the cherry, some in- 
fested leaves were placed in covered jelly glasses and the leaves 
renewed each day. These insects matured on cherry as rapidly as 
on plum, but as there were no males present they died without de- 
positing any eggs. Later observations upon the same trees at Inde- 
pendence, however, failed to reveal any eggs upon any but the plum, 
on which plant the} 7- were very numerous. Although no eggs were 
found on these trees, the fact that the aphides could grow to full size 
upon the cherry indicates that under some conditions this insect ma) 
hibernate on the various plants on which it was found at Independence. 

EMERGENCE FROM HIBERNATION. 

Whether the eggs are laid upon the plum, prune, sloe, or hop, the 
aphides emerge about the same time. The exact date was not ob- 
tained, but judging from the fact that full-grown aphides were ob- 
served April 23, and allowing 13 days for growth, they must have 
emerged from the egg about April 10. Again, allowing 26 days for 
the two generations on the prune and May 24 as the date of the ap- 
pearance of the first winged insects, the eggs must have hatched by 
April 28. This assumption corresponds very closely with data ob- 
tained at Richfield Springs, N. Y., in 1888 by Mr. Theodore Pergande, 
who observed the emergence of (he aphides from eggs on April 5, 16, 
and IS and May 10. 

The insects which emerge from the sexual eggs are wingless vivip- 
arous females — "stem-mothers," so-called. They are 1£ to 2 milli- 
meters (^ to ^V inch) in length, whitish green in color, and have 
rather long antennae set on frontal tubercles, which are provided on 
the inner side with a tooth (see fig. 2). These toothed frontal tuber- 
cles are very characteristic, of this species and serve well to identify it. 

METHOD OF REPRODUCTION . 

These viviparous insects, instead of depositing eggs, as do the sexual 
generations which appear in the fall, give birth to living young by a 
process called "budding." These young may be readily seen pro- 
truding from the tip of the abdomen. This is also the method of 



Jul. 111, Bureau of Entomology, U. S. Dept. of Agriculture. 



Plate I. 




Fig. 1.— Nymphs and Winged Forms of the Hop Aphis I Phorodon humuli) on Hop 
Leaves. (Original.) 




Fig. 2.— Winter Eggs of the Hop Aphis. Position Indicated by Arrows. ^Original.) 
STAGES OF THE HOP APHIS. 



LIFE HISTORY. 13 

reproduction of the winged migrants of both the spring and the fall 
generations. The stem-mothers arc very prolific, as shown in Table 
III, one aphis being capable of populating several leaves in a very 
shorl time. 

NUMBER OF GENERATIONS ON ALTERNATE HOST. 

Mr. Franz Remisch, of Saaz, Bohemia, who observed the emergence 
from the winter eggs, obtained two generations on plum. The writer 
did not observe the emergence of the first generation, but during the 
spring only two generations were found on prune, the second one 
being winged. In Bulletin 160 of the California experiment station 
Prof. W. T. Clarke reports the 

appearance of winged aphides "^n. / 

14 days after the first wingless ^v yf 

insects were observed. This "Vv^V X «/ 

would be sufficient time for \\ \^ /f // 

but one generation to mature. \\ \y> n n rYy / 

and it is very probable that \\ V i *y 

there are only two generations \y ^X/ 

upon the prune in the Pacific -£^/7~ \\<^\ 

region. // ^fJ- \^ \ 

MIGRATING FORMS. ' // /A.L - --_b\ \\ 

The winged or migrating JJ r/ m _ _JJ ^a ^V 

aphides, except for the pres- n j [ ill/ 

ence of two pairs of relatively I V- ' I! 

large, delicate wings, some dark 1 V> /-y I 

spots on the thorax, and a H \T1_ IT// // 

slightly more slender body ]( \f ^jf / I] 

(fig. 3 and PI. I, fig. 1) differ * P^ 

little from the wingless form. « " 

They appeared at Perkins, FlG - 2 -- Th e hop aphis (Phorodon humuiiy. wingless 

,, , , r , viviparous female. »'. really enlarged. (Original.) 

( al., May 15 and were present 

there and at Santa Rosa until June 15. Five belated individuals 
were observed at Perkins the latter part of July, but the migrations 
had taken place by the 20th of June. 

MIGRATORY ACTIVITIES. 

These winged aphides, which mature on the plum, are the first 

migrants. They are weak fliers, but when aided by a light wind 
may travel some distance. Their progeny, the wingless viviparous 
females, which are the most common forms found upon the hopvines 
throughout the season, are incapable of migration from one vine to 
another except where two vines come into contact so that the aphis 



14 



THE HOP APHIS IN THE PACIFIC REGION. 



can crawl from one to the other. The winged forms, therefore, are 
the only ones that migrate during the spring and early summer. 

In the fall the winged form (fig. 3) that produces the sexual female 
migrates from the hop to its winter host — the plum, prune, sloe, or 
hop — and later the winged male migrates to the plant on which the 
sexual female awaits fertilization. 

In the rearing cages and in the field during 1912 winged forms did 
not appear except as noted above. Winged forms were observed, 
however, developing upon the hopvines during the summer, at Wat- 
sonville, Cal., by Prof. W. T. Clarke, of the California Experiment 
Station, in 1902; by Mr. Franz Remisch, at Saaz, Bohemia; by Mr. 
H. N. Ord, at Independence, Oreg.; and by the writer at Santa Rosa, 
Cal., in 1911. 

As previously stated, the winged migrants are weak fliers, but when 
aided by the wind may travel some distance. Some individuals were 




Fig. .".—The hop aphis: Winged female migrant. Much enlarged. (Original.) 

found half a mile from the infested prune trees. The infestation, how- 
ever, decreases as the distance from the alternate host increases. 

It was observed that more migrants collect upon the taller vines 
and the upper, newly expanded leaves of the other vines than upon 
the lower matured leaves. Very few winged aphides were observed 
on the fully expanded and hardened foliage, but were in every case 
some distance from the ground. The lower leaves were entirely 
free from the winged forms. 



DEPOSITION OF YOUNG. 



Upon reaching the hopvines these parthenpgenetic migrants were 
observed giving birth to young, the number deposited by each indi- 
vidual varying between 1 and S, as is shown in Table I. 



LIFE HISTORY. 15 

Tain i: 1 . /{utcaj'tlrposltimi of young by iri ngtd in i grants of thehop aphis from prune trtes. 





Date and number deposited. 


Total. 




Maj 28. 


May 29. 


May 30. 


May 31. 


June 1. 


June 3. 




2 

2 


4 
2 

:; 
4 


1 


1 






7 




1 

i 



1 




a 














1 






a 








j 










2 


1 


3 








1 





























! 




1 







The data in Table I were obtained by isolating nymphs, taken 
from the prune trees, upon clean prune leaves in covered jelly glasses. 
When the winged insect appeared 
it was immediately placed upon a 
hop leaf. The deposited young 
were removed daily. 




5mc/ 




Fig. 4.— Head of hop aphis, showing frontal tuber- 
cles. Greatly enlarged. (Original.) 



Fig. 5. — Head of melon aphis {Aphis gossypii). 
This aphis is frequently found on hops. Note 
differences in head from that of hop aphis. 

(ireally enlarged. (Original.) 



These young deposited by the 
winged aphides are wingless par- 
thenogenic insects (PI. II, fig. 1). They have the characteristic frontal 
tubercles (see fig. 4, in comparison with fig. 5) and vary in color from 
watery white to green. The very young insects and those that have 
just molted are very light, while the older ones may be quite green. 

RATE OF GROWTH. 

These young aphides grow very rapidly, molt four times, and 
immediately after the fourth molt commence depositing their young, 
as shown in Table II. 





Table II. — Stages in the development ofth 


' wingless vivipai 


ous female hop aphis. 


No. 


De- 
posited. 


First 
molt. 


Second 
molt. 


Third 
molt. 


Fourth 
molt. 


Com- 
menced 
depositing 

young. 


Total 
days. 


1 


June 11 
15 


June 13 

17 

IS 

m 

21 


June L5 
20 
21 
21 
23 
24 


June 17 
23 
23 
23 
26 
26 


June 19 
25 
26 

25 

2S 

28 


June 20 9 


2 


27 12 




27 12 


4. 




16 

is 

is 


27 11 
29 12 


6. 




29 


12 



16 



THE HOP APHIS IN THE PACIFIC REGION. 



From these experiments, which were conducted with individual 
insects, it was found that a period of from 8 to 12 days is required 
for the aphides to pass through the four molts and begin depositing 
young. 

NUMBER OF YOUNG DEPOSITED BY VIVIPAROUS FEMALES. 

Some of the experiments that were carried on to determine the 
number of young that are deposited by individual aphides are 
recorded in Table III. 



Table III. — Number of young deposited by each of 12 individuals of the hop aphis. 



Date. 


Number of young deposited by — 


No. 1. 


No 2.. 


No. 3. No. I. 


No. 5. No. 6. 


No. 7. 


No. 8. No. 9. 

1 


No. 10. 


No. 11. 


No. 12. 




4 
5 
7 
4 

2 
4 
2 

3 
















1.3 






















4 
3 
2 
3 
3 
4 
4 


1 

3 
3 
4 
5 
3 
5 
4 
3 
3 

5 
































Hi 

































IS 














10 
















1 

3 
4 
2 

4 
3 
6 
5 
2 
6 

3 
3 
3 
2 














21... 


1 
3 
3 
4 
3 
7 
5 
2 
8 
2 
1 
5 
3 
3 



3 
2 
S 
3 
3 
3 
2 
3 
5 

G 
4 

G 

2 
3 
2 
2 
5 
2 
4 
3 
2 
1 














22 


2 
2 
2 

4 
G 
5 
5 
8 
4 
4 
G 
5 
4 
4 

3 

4 


2 
3 

2 
3 
9 
4 

6 

7 
1 
2 
3 
3 
6 
4 
2 
5 
1 
1 
2 


2 
4 

4 
4 
4 

5 
5 
G 
5 
4 
G 
3 

7 
5 
1 
3 

1 



















24 


3 
5 
3 
3 

5 
4 
1 


3 
3 
4 
4 
9 
3 
5 
2 
3 








25 
















27 


1 
4 
2 

i 

3 

4 

4 
4 
3 

1 
4 

1 

1 
1 






28 


2 

4 
1 
8 

2 
2 
4 


1 


1 


3 




1 


30 




July 1 




5 


2.. . 











4 


o 3 


6 

5 











4 

3 
G 
5 
1 

2 
2 
3 


4 






























I 


10.. 











12 










13 








o 


14... 








j 






















u; . 




















































































43 


53 1 92 


87 


70 


73 


S7 


38 


29 


51 



















In order to obtain the foregoing data nearly mature aphides were 
isolated on hop leaves in tin-covered jelly glasses. The leaves were 
changed daily and the aphides which had been deposited were 
removed. The number of young which are deposited by one stem- 
mother were thus found to be from 29 to 92, with an average of 64 
for the 12 aphides under observation. The length of life of these 
aphides varied from 25 to 38 days, with an average of 30.75 days. 
Thus an aphis living an average life of 30.75 days, depositing an 



LIFE HISTORY. 17 

average number of young (3.3 per day) over an average period of 
19 days, would give birth to 63 aphides. 

At this rate of reproduction, provided that none of the aphides 
wore destroyed before they had lived an average life, one winged 
aphis which settles on the hop in the spring would at the end 
of the fifth generation be the parent of 4,068,989,826 living aphides. 
These aphides would weigh 2,152 pounds. From these figures the 
very sudden and extensive infestations by this insect are readily 
explained. 

THE FALL MIGRANTS. 

The nymphs of the fall migrants (fig. 6) became winged in the breed- 
ing cages at Perkins, Cal., on Au- 
gust 26 and in the field August 
28. Migrants were observed 
upon plum at Independence, 
Oreg., September 22, 1912. 
Young were being deposited \ 

there and upon the next visit 
to the locality, October 16, large 
numbers of male aphides were 
observed copulating with the 
sexual females that had been 
deposited by the migrants. 
Many eggs were also present at /< 

this time. -r 

THE WINTER EGG. 

The winter egg, when first H \ c ^~~]~~-j \\ 

deposited, is a shiny-green ob- \\ lk-~k\ it 

ject, ovate in shape, and a little 
smaller than the head of a pin 
(| mm. in length). Soon, how- FlG - 6 - — The h °P a P his: N >' m P h > showing wing-pads. 

, . , Greatly enlarged. (Original.) 

ever, it turns dark green and 

then black and appears as a shiny-black point (PI. I, fig. 2) on the 

branch of the alternate host plant. 

The eggs are usually deposited close around the buds or on the rough 
leaf scars, but may sometimes be found upon the smooth parts of 
the twigs. 

THE LIFE CYCLE. 

The entire life cycle where the writer's observations were made is 

as follows : Two generations occur on the alternate host, the second 

one being winged. Five and six generations occur on the hop, a 

part of the fifth becoming winged and depositing young upon the 

74956°— Bull. 111—13 3 




18 THE HOP APHIS IN THE PACIFIC REGION. 

alternate host, and part being wingless and depositing young (sixth 
generation) upon the hop, producing the male aphides which fly to 
and copulate with the young deposited on the alternate host by the 
winged individuals of the fifth generation. These fertilized females 
deposit the winter eggs, which, hatching in the following spring, 
produce the viviparous insects for that season. 

Table IV gives one series of dates for the life cycle. This series 
will vary according to the date of the emergence of the first generation 
from the egg in the spring. The variation in the date of hatching of 
the winter eggs causes an overlapping of generations, so that these 
are not in the least distinct. 

Table IV. — Life cycle of the hop aphis as observed a I f'erkins, Cal., in 1912. 

Emergence from eggs June 3 

Appearance of second generation, winged .June 17 

Appearance of third generation (first on hops) June 30 

Appearance of fourth generation (second on hops) July 11 

Appearance of fifth generation (third on hops) July 22 

Appearance of sixth generation (fourth on hops) Aug. 2 

Appearance of seventh generation (fifth on hops), part winged Aug. 15 

Appearance of eighth generation (sixth on hops), males Aug. 25 

Appearance of eighth generation, sexual females, on plum Aug. 25 

Deposition of eggs Sept. 14 

In the report of the Department of Agriculture for 1888, Prof. C. V. 
Riley gives the following data upon the life history, which vary 
somewhat from the data given in this bulletin: 

Three parthenogenic generations are produced upon Prunus, the third being winged. 
* * * A number of parthenogenic generations are produced upon the hop until 
in autumn, and particularly during the month of September winged females are again 
produced. 

This account is also at variance with the writer's own observations 
in that no winged forms are noted during the summer. 

THEORY REGARDING SUMMER MIGRANTS. 

The presence of winged forms of the hop aphis throughout some 
seasons and the absence of such forms during 1912, both in the 
laboratory and in the field, except at the end of the fifth generation, 
are explained as follows: The eggs of the hop aphis have been ob- 
served to hatch individually during a period of one month and five 
days, April 5 to May 10. The winged forms were observed beginning 
to migrate from the prune May 24, and migration was not completed 
until June 20. Thus until the 20th of June migrants from the 
alternate host (the plum or hop) were present in the hopyards. 
Beginning the life cycle with the first insects that migrated, the 
seventh or winged generation on the hop would be mature July 19. 
These insects, finding some tender hop leaves upon which to settle, 



HABITS. 19 

would deposit young thereon. The deposited young, because of 
climatic and succulent food conditions, might become viviparous 
instead of oviparous, causing a continuous increased infestation of 
the hopvines. 

At Perkins and Santa Rosa, Cal., in 1912, a hot, dry wind early in 
the season destroyed practically all of the aphides which came from 
the alternate host, and it was the progeny of the later migrants 
which became winged. 

These data have not been proven, but remain as the only explana- 
tion of the presence of winged aphides between the spring and fall 
migrations. 

Since the first insects that migrate to the hop are probably the 
progenitors of the winged forms that occur during midsummer, it is 
evident that the control of the aphis early in the season will tend to 
reduce the numbers of the winged insects and therefore lessen the 
chance that thoroughly sprayed yards will become reinfested. 

HABITS. 
HABITATION. 

Hop aphides are usually found on the underside of the leaves 
(PI. II, fig. 1), but in cases of severe infestation they may be found on 
the upper surface as well. They gradually work up the vines, and 
when the hops have formed many of them may be observed inside 
of the cones. 

PROTECTION. 

Many of the aphides, especially in cases of slight infestation, will 
be found close to the veins and in the hollow parts of the leaves. 
Here, besides being protected by the sheltering leaf, they are partially 
protected by the surrounding wall of leaf. Other than the natural 
formations of the leaves the hop aphis has no protection from wind, 
rain, or enemies. 

RELATION OF ANTS TO THE HOP APHIS. 

At Perkins, and especially at Santa Rosa, Cal., a large black ant, 
Formica subsericea Say, was continually observed among the aphides. 
The habit of the ants in caring for plant lice that they may feed 
upon the honeydew excreted by them is historical. These ants 
carry the aphides to the newly expanded leaves, thus spreading the 
infestation. They were so active at Santa Rosa that it was found 
necessary to put tree tanglefoot on the vines that were used for the 
experiments, to prevent the ants from reinfesting them. 



20 



THE HOP APHIS IN THE PACIFIC REGION. 



FIRST APPEARANCE OF THE HOP APHIS IN THE SEASON. 



The first wingless viviparous, aphides of the season at Santa Rosa, 
Cal., at Independence, Oreg., and at Agassiz, British Columbia, 
were invariably observed upon hopvines near shrubby growth 
bordering a watercourse or fence, near a sheltering tree, or near 
buildings. At Santa Rosa and Agassiz, where the writer made 
observations during the early part of the season, the aphides were 
most numerous near shrubbery or buildings, the numbers decreasing 

as the center of the 






30 


uo 


LO 80 .ft 




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20 


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10 


40 




SO 


/o 


30 


30 


SO 




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/o 


V 





d 


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/o 


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d>~ 


i 


to 


o 


4 


o 


4 


4 


8 


2 





2 





2 


f.... , 


* 



Fig. 7.— Diagram showing relative number of aphides in different 
parts of a single hopyard, indicating the increased infestation 
near Santa Rosa Creek (a). (Original.) (The numbers repre- 
sent approximate counts of aphides which were present on the 
vines June 1, 1911. On September 1 these vines were grossly 
infested. The row nearest the creek (a) is row 1; the next is 
row 2; and after that the numbers were taken from every fifth 
row. Each number represents the number of aphides found on 
the hill in that location.) 



and the 

weather. 

A hot, 

sections, 



most severe infestations occur 



field was approached. 
This condition is 
shown diagrammati- 
cally in figure 7. In 
fact, at Santa Rosa 
on May 30, 1911, and 
June 6, 1912, the 
aphides occurred in 
numbers only near the 
brush, trees, or build- 
ings, the other parts 
of the field being al- 
most entirely free. 

FAVORABLE AND 
UNFAVORABLE 
CONDITIONS FOR 
THE APHIS. 

Moderately warm, 
moist seasons with an 
occasional rain but 
with little strong wind 
are the most favor- 
able for the develop- 
ment of the hop aphis, 
during seasons of such 



dry wind is very unfavorable to the aphides and in some 
when followed by dry, warm weather, will materially 



check infestation. 



EFFECT OF HEAT. 



Some careful observations on the condition of the hop aphis after 
continued hot weather, and especially when the hot weather was 
accompanied by a north wind, were made at Perkins, Cal. 



3ul. Ill, Bureau of Entomology, U. S. Dept. of Ag 



.... 


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Of 




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fci 






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f ( K 


VI 

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wft^ 


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<o([ jhm|^^,^ *£ J99V^ 


ff$J 



Fig. 1.— Wingless Progeny of Winged Hop Aphides from Alternate Host. 
(Original.) 




Fig. 2.— Willows Along Edge of Hopyard, which were Erroneously Supposed 
to Harbor Hop Aphides. 'Original.) 



THE HOP APHIS. 



of Entomology, U. S. Dept of Agriculture 




Plate II 



Fig. 1.— Upper Row, Normal Hop Cones; Lower Row, Hop Cones Injured by the 
Hop Aphis. (Original.) 










Fig. 2.— Vines in Foreground Severely Injured by the Hop Aphis Showing Lack 
of Growth as Compared with Uninjured Vines in the Distance. (Original.) 

INJURY TO HOPS AND HOPVINES BY THE HOP APHIS. 



Bureau of Entomology, U. S. Dept. of Agriculture 




Fig. 1.— Hopvines Severely Injured by the Hop Aphis, and Left in the Field. 
(Original.) 




Fig. 2.— Enlarged View of Damaged and Moldy Hopvines. (Original.) 
INJURY TO HOPVINES BY THE HOP APHIS. 



Bui. 111, Bureau of Entomology, U. S. Dept. of Agr 




Fig. 1.— Eggs of Hippodamia convergens Among Hop Aphides on Leaf. (Original. 



i»* 






Fig. 2.— Syrphus Fly Larv/e Feeding upon the Hop Aphis. (Original.) 
SOME NATURAL ENEMIES OF THE HOP APHIS. 



NATURE OF DAMAGE. 21 

It was noticed that in every case where the aphides were reduced 
by the effect of the heat, some small ones remained and upon ma- 
turing produced the following generation. In some cases not a 
single full-grown aphis was found after the hot weather had ceased, 
but many of the young aphides were present upon the vines. A 
similar observation was made at Santa Rosa, Cal. 

FOOD PLANTS. 

Phorodon humuli feeds principally upon the hop. It has, however, 
some alternate food plants on which the sexual forms develop. (See 
p. 14.) 

It is a common belief that the aphides found upon the shrubs and 
trees growing near the hopyards (see PI. II, fig. 2) are hop aphides 
and that they later migrate to the hops. Specimens of aphides were 
taken from various plants growing near the hopyards at Agassiz, 
British Columbia, Independence, Oreg., and Santa Rosa, Cal., and 
identified. In no case was Phorodon humuli found among the aphides 
collected. Even though aphides may be extremely numerous upon 
such near-by plants, they do not in the least menace the hop crops; 
hence their destruction, from the standpoint of hop-aphis control, is 
unnecessary. 

NATURE OF DAMAGE. 

GENERAL EFFECT OF APHIDES UPON HOPS. 

The hop aphis injures the crops in two ways: By extracting the 
plant juices it prevents the normal growth of the plant, and by the 
excretion of honeydew, on which grows the black-smut fungus, 
Cladosporium sp., it injures the quality of the crop. 

In one hopyard at Santa Rosa, Cal., May 31, 1911, several vines 
were found which were severely infested. Later in the season these 
vines were observed to have made little growth. The few hop cones 
which had formed were very small, some being only slightly larger 
than the burrs. Plate III, figure 1, shows some of these small cones 
compared with normal cones which were taken from near-by unin- 
fested vines. The relatively small growth of the infested vines com- 
pared to that of the uninfested vines is well illustrated in Plate III, 
figure 2. The vines in the foreground were severely injured by the 
aphides, while those farther back were only slightly infested until 
late in the season and made a very fair growth. 

Some vines that were only slightly infested were observed through- 
out the season. These vines grew well ami bore a fine crop of hops, 
but just before the harvest the aphides entered the cones, extracted 
their vitality, and covered the scales with honeydew, in which the 
black-smut fungus soon established itself. These cones were so 



22 THE HOP APHIS IN THE PACIFIC REGION. 

severely injured that they were not worth picking, and they were left 
in the field. (See PI". IV, figs. 1, 2.) 

Where control work is attempted the infestation seldom becomes so 
severe as to retard the growth of the vines, and it is the late injury — 
the accumulation of honey dew upon the cones and the resulting 
growth of the black fungus — which is most to be feared. 

IIONEYDEW AND ITS EFFECT ON THE HOPS. 

Honeydew is a substance which is excreted from the anal opening 
of the aphides. It is composed largely of gums and sugar and is 
sticky and sweet to the taste. On warm afternoons it may be seen 
falling as a mist from severely infested vines. 

Hops covered with honeydew are sticky, do not have the normal 
amount of crispness, and when pressed between the fingers remain 
flattened out. Honeydew may under some circumstances increase 
the weight of the crop. One grower estimated that ho made $1,000 
on honeydew in 1911. However, the quality of the crop was greatly 
injured, and had the demand for hops been less the grower would not 
have been able to sell, and his crop would have been a complete loss. 

Even though under certain uncontrollable circumstances the pres- 
ence of honeydew may increase the income from a crop of hops, their 
quality is injured, and the honeydew is the medium for the black-smut 
fungus, which will, in ninety-nine cases out of one hundred, so injure 
the quality of the crop that it will be unsalable. 

BLACKENING OF HOPS. 

Neither the honeydew nor the aphides are directly responsible for 
the blackening of the hops. The blackening is due to a smut fungus 
{Cladosporium sp.) commonly called "mold," which grows upon the 
honeydew. If the honeydew happens to be upon the hop cones, this 
fungus gives the hops a black, moldy appearance, which is extremely 
undesirable. 

NATURAL ENEMIES. 

Several predaceous insects have been observed attacking the hop 
aphis at Perkins and at Santa Rosa, Cal. The ladybirds Hlppodamia 
convergens Guer., Coccinella calif braica Mannh., Cocci nella abdominalis 
Say, and Chilocorus orbus Cas. were frequently found among the 
aphides. Some eggs of Hippodamia convergens deposited among the 
hop aphides are shown in Plate V, figure 1. Chrysopa calif ornica 
Coq. was always abundant in the hop fields, and the larvae were 
very active in feeding upon the aphides. 

The larvae of syrphus flies (PI. V, fig. 2) were abundant in the 
hopyards. Syrplms opinator O. S. and Syrphus ameiicanus Wied. 
were reared from the larvae which were collected from hop leaves. 



CONTROL OF THE HOP APHIS. 23 

A small predaceous bug, Triphleps insidiosus Say, was occasionally 
observed among the aphides. 

The following insects were observed by Mr. Theo. Pergande attack- 
ing the hop aphis at Richfield, N. Y., in 1887: 

THphleps insidiosus Say Camptobroehis nebulosus Uhl. 

Adalia bipunctata L. Anthocoris ep. 

Sicthorus punctum Lee. 

Parasites and predaceous insects destroy large numbers of hop 
aphides, but in no case have they been observed successfully to con- 
trol an infestation. 

CONTKOL OF THE HOP APHIS. 

AXIOMS OF SUCCESSFUL CONTROL. 

In the economic control of the hop aphis, as of other insect pests, 
there are certain underlying principles which must be adhered to if 
the work is to be entirely successful. 

(1) All of the machinery to be used must be capable of doing 
effective work and must be in good working condition prior to the 
time at which spraying should commence. 

(2) Spraying must commence at the proper time; it must not be 
put off. 

(3) The material used must be carefully prepared and thoroughly 
but not wastefully applied. 

These are fundamental principles, and control work will be less 
effective and more costly if they are not closely adhered to. 

INSECTICIDES USED. 

Several contact insecticides have been used to control the hop 
aphis. The most extensively used sprays, however, are tobacco 
decoctions with whale-oil soap and quassia chips with whale-oil soap. 
In order to obtain exact data upon the effectiveness of these materials 
upon the hop aphis a series of experiments on a small scale was con- 
ducted at Santa Rosa, Cal., and notes were taken from experiments 
made on a large scale in Oregon. Tag counts were made; i. e., 20 tags 
were tied to as many leaves, and records of the number of aphides 
on the leaves before and three days after spraying were made on the 
tags; the percentage of aphides killed was thus accurately obtained. 

TIME TO BEGIN SPRAYING. 

It is very desirable to spray all plums or prunes that are infested by 
hop aphides as soon as the infestation is observed, both in the fall and 
hi the spring. This will check the migration and lessen the infestation 
of the hops. The hops, however, should be sprayed as soon as the 



24 THE HOP APHIS IN THE PACIFIC REGION. 

aphides become numerous. This is usually from June 1 to 15, though 
in some cases it may be earlier. It is well to spray first the fields wliich 
are most seriously infested. 

It is usually desirable to wait until the vines are stripped before 
spraying. 

NUMBER OF APPLICATIONS. 

The number of applications which are necessary to control the 
aphides will vary with the seasonal and local conditions. The object 
is to prevent injury to the vines and to have the vines practically free 
of aphides at the time hop picking commences. To obtain good re- 
sults it is usually necessary to spray the vines from two to four times. 

NECESSITY FOR EARLY SPRAYING. 

Mr. H. N. Ord, who directed some very successful spraying opera- 
tions in a large hopyard in Oregon, claims that the secret of his 
success was early spraying. He began before the aphides became 
very numerous and continued as long as there were any aphides in 
the field. Yards sprayed under Mr. Ord's direction were practically 
free from aphides, while the crops of a near-by grower were so severely 
damaged that 10 acres were left in the field unpicked. 

NECESSITY FOR THOROUGH WORK. 

The insecticides which are used for the hop aphis kill only by actual 
contact, and if satisfactory results are to be obtained it is absolutely 
necessary that the spray be thoroughly applied. Running the spray 
up and down the vine is not sufficient, because all of the leaves must 
be thoroughly wetted on both surfaces if good results are to be 
obtained. 

PROCRASTINATION . 

In sections where the aphides are frequent!}' controlled by weather 
conditions some growers are likely to delay control work, hoping that 
a hot, dry wind will relieve them of the necessity of spraying. In one 
hop-growing section of California such a wind has appeared regularly 
for several years, but during the past two seasons (191 1-12), which were 
favorable for the aphides, it did not arrive. Many growers, depending 
upon this wind, made no effort to control the aphides until late in the 
season, when much damage had been done. It was then difficult to 
make much progress against the insects, and severe injury resulted. 

SPRAYING EXPERIMENTS. 

The nicotine solutions appeared to be the most promising materials 
and were therefore the most extensively used in the experi- 
ments. The following tables, arranged according to relative costs, 



CONTROL OF THE HOP APHIS. 



25 



show the results of these experiments and give the cost of the mate- 
rials per 100 gallons of spray: 

Table V. — Results of spraying experiments for the hop aphis, with costs of materials 
per 100 (jul Ions of spray. 



Expert 



Mali-rials used. 



Nicotine sulphate, 1 to 3,000 

Nicotine sulphate. 1 to 2,000 

Nicotine sulphate, 1 to 3,000; 

whale-oil soap, 4 to 100. 
Nicotine sulphate, 1 to 3,000; 

cresol soap, 1 to 300. 
do 



B lack leaf tobacco, 1 to 75 

Nicotine sulphate, 1 to 2,000; 
cresol soap, 1 to 300. 

Blackleaf tobacco, 1 to 60 

Nicotine sulphate, 1 to 1,000 

Nicotine sulphate, 1 to 2,000; lye- 
resin soaps. 

Nicotine sulphate, 1 to 1,000; 
whale-oil soap, 4 to 100. 

Nicotine sulphate, 1 to 1,000; 
cresol soap, 1 to 300. 



, Number 
Pressure. of 

aphides. 



Pounds. 
80 LOO 
80 100 

80-100 

80-100 

80-100 
80-100 
80-100 

80-100 
80-100 
so 100 

80-100 

80-100 



1 , 227 
1,005 
3,089 



'654 
2,225 

2,512 

2,780 



Per cent 
killed. 



Date 
sprayed. 



June 15 
June 13 
June 14 



...do.... 
...do... . 
...do.... 

...do.... 

June 13 
June 15 

June 14 

June 15 



Date 

counted. 



June 
...do. 
...do. 



..do. 

..do. 
..do. 

..do. 
..do. 
..do. 

..do. 

..do. 



Cost per 

100 gal- 
lons. 



$0.4lti 
.62 
.80 



1.08 
1.25 
1.37 

1.42 

1.67 



INEFFECTIVE MATERIALS. 



13 Limesulphate, 36° Baume, 1 to86. 

14 Cresol soap, 1 to 300 



80-100 
80-100 



1.950 
129 



June 16 
June 13 



June 19 
June 16 



SO. 24 
.42 



From the data in Table V it is evident that all the experiments 
except Nos. 5, 13, and 14 were quite satisfactory and that Nos. 1, 
2, 3, and 4 were the cheapest materials to use. It was found that 
the nicotine sulphate without soap did not spread very readily and 
that the good results obtained were due to the very careful applica- 
tion. Either flour paste or soap should always be used with the nico- 
tine solutions. 



Table VI. — Spraying experiments conductea]in Oregon against the hop a phis during 1911. 



< «1 

£.«' Materials used. 
«1 


: Number 
Pressure. of 

1 aphides. 


Percent Date 
killed. sprayed. 


Date 

counted. 


Cost per 
100 

gallons 


1 
2 
3 


Tobacco waste, 25 pounds to 100 

gallons water. 
Tobacco waste, 27i pounds to 100 

gallons water. 


Pounds. 

100 

100 
100 

100 

100 

100 
100 


213 

253 

695 

529 
73 

491 
130 


100 Aug. 22 

100 ...do 

89 Aug. 21 

98 ...do 

100 ...do 

98 L.dO 

97 Aug. 22 


Aug. 25 

Aug. 24 

Aug. 23 

...do 

...do.... 

...do 

Aug. 25 


$0. 18 
.20 
.62 


4 
5 


Nicotine sulphate, 1 to 2,000; whale- 
oil soap, 5 to 100 


. 845 
1.25 


6 


Nicotine sulphate, 1 to 2,000: whale- 
oil soap, 5 pounds to 100 gallons 


1.475 


7 




1.66 









26 THE HOP APHIS IN THE PACIFIC REGION. 

Tabic VI represents the work done in Oregon by Mr. H. N. Ord 
and is in part a repetition of the results recorded in Table V. It 
also contains data upon tobacco waste, which appears very satisfac- 
tory and very cheap. If the decoction is allowed to boil or the tobacco 
happens to be low in nicotine, the spray will not be effective, and the 
vines will have to be resprayed. 

If this material be used each tankful should be tested upon some 
aphides and a record of efficiency kept. It is for these reasons not so 
satisfactory as a material containing a known quantity of insecticide. 

XUotim -sulphate formulas for 100-gallon lots. 

Ounces. 

Nicotiuo sulphate, 1 to 1.000 13 

Nicotine sulphate, 1 to 2,000 6£ 

Nicotine sulphate, 1 to 2,500 51 

Nicotine sulphate, 1 to 3,000 4 J 

The formula "4-100," given for flour paste, means 4 gallons of 
flour paste (made according to directions) to each 100 gallons of spray. 
This paste contains 1 pound of flour in each gallon, so that there 
would be 4 pounds of flour (in the form of paste) in each 100 gallons 
of spray. 

The formula " 4-100," when referring to whale-oil soap, means 4 
pounds of whale-oil soap to 100 gallons of spray. 

Flour paste had proved to be a most efficient, cheap, and convenient 
spreader for the lime-sulphur solutions. 1 Some experiments were 
conducted during 1912 with this material in combination with nico- 
tine sulphate against the hop aphis. Table VII gives some of the 
results obtained with this mixture. 

Table VII. — Experiments in the control of the hop aphis by sprays of nicotine sulphate 
and flour paste. 



Number 




of 


Per cent 


aphides 


killed. 


present. 




6?7 


100 


611 


100 


1,668 


99 


148 


99 


308 


100 


271 


96 



Cos' per 
100 

gallons. 



Nicotine sulphate, 1-2,000; flour paste, 4-100 

Nicotine sulphate, 1-2,500; flour paste, 4-100 

Nicotine sulphate, 1-3,000; flour paste, 4-100 1, 668 99 .50 

Do 148 99 .50 

Nicotine sulphate, 1-3,500; flour paste, 4-100 308 100 .45 

Nicotine sulphate, 1-4,000; flour paste, 4-100 271 96 .40 



From the results noted in the preceding tables it is evident that 
nicotine sulphate is effective in dilutions as high as 1-3,500, and that 
flour paste, 4-100, is an effective spreader for this material. The 
nicotine sulphate, 1-4,000, was not quite so effective, and it was also 
observed that its action was so slow that the sprayed aphides were 
able to deposit young on the leaves, thus reinfesting the hopvines. 



Bulletin No. 117 anil Circular No 166 of this bureau. 



CONTROL OF THE HOP APHIS. 27 

Nicotine sulphate, 1-3,000 and 1-3,500, in combination with 
whale-oil soap or flour paste has been successfully used in experi- 
ments, but jt would be safer in practice to use the lower dilutions. 
1 n case the greater dilutions are used, careful observations should be 
maintained to be sure that the spray is doing effective work. The 
nicotine preparations which come in cans have a slight tendency to 
settle. In case they do settle and are not thoroughly mixed before 
measuring, the percentage of active insecticide used in one lot of 
spray may be enough less than should be present in a uniform portion 
to render the spray ineffective. It is advisable, therefore, to be sure 
that these preparations are thoroughly mixed before measuring. 

MIXING NICOTINE SOLUTIONS AND WHALE-OIL SOAP. 

During certain spraying experiments with tobacco extracts and 
whale-oil soap some difficulty w T as experienced in mixing the concen- 
trated solutions of blackleaf tobacco and whale-oil soap. When 
these were combined a greenish-gray precipitate of a flocculent nature 
was formed. A similar precipitate occurred when one of the mate- 
rials was diluted and the other left concentrated. When each solu- 
tion was diluted to half of the final amount, however, this objec- 
tionable nozzle-clogging precipitate did not appear. 

Flour paste does not have this effect, but when whale-oil soap is 
used as a spreader for tobacco sprays, both solutions must be well 
diluted before mixing. 

PREPARATION OF THE FLOUR PASTE. 

In preparing the flour paste, mix a cheap grade of wheat flour 
with cold water, making a thin batter without lumps, or wash the 
flour through a wire screen w T ith a stream of cold water. Dilute until 
there is 1 pound of flour in each gallon of mixture. Cook until a 
paste is formed, stirring constantly to prevent caking or burning. 
(See PI. VI, fig. 1.) Add sufficient water to make up for evaporation. 

If the paste is not sufficiently cooked, the resulting spray will not 
be effective. If overcooked, the paste will harden when thoroughly 
cool; it will then not mix with water very readily. Usually, how- 
ever, the paste is used as it is prepared, and overcooking is not a 
disadvantage. 

W T hen mixed in a spray tank flour paste has a tendency to settle, 
and in order to do satisfactory work agitation is necessary. This is 
only a slight disadvantage, however, and is necessary with most spray 
materials. The large spray tanks are usually fitted with an agitator, 
and a hoe makes an effective agitator for the 50-gallon barrels, so that 
this problem is a simple one. 



28 THE HOP APHIS IN THE PACIFIC REGION. 

ADVANTAGES OF FLOUR PASTE OVER WHALE-OIL SOAP AS A SPREADER 
FOR CONTACT INSECTICIDES. 

Flour paste costs 8.8 cents per 100 gallons of spray. Cheap flour 
is always available, and the paste has no odor. Whale-oil soap costs 
20 cents per 100 gallons of spray, is not always available, and has 
a disagreeable odor. 

Both materials have to be heated before using. 

The neutrality of flour paste was proven by the fact that when 
applietl upon the foliage and blossoms of the hop, in proportions as 
high as 12 gallons of paste to 100 gallons of spray, no injurious 
effects resulted. When sprayed upon the hop burrs and delicate hop 
cones, it did not prevent pollination or injure the appearance of the 
scales. 

QUASSIA. 

Quassia is the extract from the wood of Picrsena excelsa, a tree 
occurring in Jamaica and containing the alkaloid quassin (C 32 H 42 O 10 ) 
in the form of crystalline rectangular plates. Quassia chips contain 
no tannic acid. 

EFFECT OF QUASSIA ON APHIDES. 

A solution of quassia containing the extract from 5.33 ounces of 
quassia chips in 1 quart of water was diluted one-half and sprayed 
on Ilyalojiterus pruni on prune. It was found necessary to wash 
the waxy pulverulence from the insects before they could be wetted. 
The leaves were tagged with the numbers of aphides present and the 
twigs set into water in the laboratory. A check branch was sprayed 
with pure water. That the strong quassia solutions have a decided 
insecticidal value is shown by the following data: 

Aphides present before spraying, 37, 40, 109, 92, 190, 75, 140, 40; total, 723. 
Aphides present after spraying. 0, 30, 3, 1, 0, 25, 0, 0; total, 59. 
Percent killed, 92. 

Quassia solution at the rate of 7 pounds of chips to 250 gallons of 
water was applied to the aphides with the following results: 

Aphides present before spraying, 48, 60, 30, 40, 73, 30, 200, 100, 63, 128, 12; total, 784. 
Aphides present after spraying, 0. 0, 5, 0, 0, 0, 1, 2, 7, 9, 10; total, 34. 
Per cent killed, 96. 

The aphides on sprayed leaves turned brown when dead. The 
check leaves contained living insects only. 



111, Bureau of Entomology, U. S. Dept. of Agriculture. 



«M 






m 






&b* 


/3HBT > 




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y ffi 

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Fig. 1.— Hindu Laborer Cooking Flour Paste. (Original.) 




Fig. 2.— Boiling and Mixing Plant Used at Independence, Oreg. (Original.) 
FLOUR PASTE AGAINST THE HOP APHIS. 



CONTROL OF THE HOP APHIS. 29 

THE USE OF QUASSIA. 

Various formulas for quassia spray are used in the field and were 
observed to be effective when properly prepared. Some of them are 
as follows: 

Formula No. 1. 

Cents. 

Quassia chips, 7 pounds, at 5\ cents per pound 37 

Whale-oil soap, 9 pounds, at 4£ cents per pound 40.5 

Water, 250 gallons. Total cost per 100 gallons 31 

Formula No. 2. 

Cents. 

Quassia chips, 8 pounds, at b\ cents per pound 42 

Whale-oil soap, 6 pounds, at A\ cents per pound 27 

Water, 100 gallons. Total cost per 100 gallons 69 

Formula No. S. 

Cents. 

Quassia chips, 9 pounds, at h\ cents per pound 47.2 

Whale-oil soap, 6 pounds, at 4i cents per pound 27 

Water, 100 gallons. Total cost per 100 gallons 74. 2 

Formula No. 1 was used by Prof. W. T. Clarke in his work upon 
the hop aphis at Watson ville, Cal., in 1902. It was also successfully 
used by the writer in some field experiments at Santa Kosa, Cal., 
during 1911. The other formulas are stronger and have also been 
observed to be effective when properly prepared. 

PREPARATION. 

Many failures in control work, when quassia is used, are due to 
faulty preparation of the material. Some growers only soak the chips 
and use what sbaks out. Others boil them without previous soak- 
ing. The proper way to prepare quassia spray, based on Formula 
No. 1, is as follows: 

Soak the chips 24 hours, then boil for 2 hours in 3 gallons of water. Add this 
decoction to 247 gallons of water in which the soap has been dissolved. The whale- 
oil soap is readily dissolved by boiling in a small amount of water. 

QUALITY OF QUASSIA. 

The quality of quassia may vary and the percentage of quassin 
which can be extracted from the different grades of chips will not 
be the same. For this reason the use of quassia chips is not so 
certain in its results as a material containing a known amount of 
insecticide. When the quassia chips are used, it is well to look 
over sprayed areas three days after they are sprayed to be sure that 
the spray has been effective. 



30 



THE HOP APHIS IN THE PACIFIC REGION. 



QUASSIA EFFECTIVE ONLY BY CONTACT. 

There is an erroneous impression among some growers that the 
quassia spray after it has dried upon the leaves will kill the aphides 
which later appear upon them. The quassia, as well as the other 
sprays used for the hop aphis, is effective only when in actual contact 
with the insects. 



EFFECT OF SPRAY MATERIALS UPON THE QUALITY OF SPRAYED HOPS. 

It was suggested by some growers that nicotine sulphate, whale- 
oil soap, and quassia extract might injure the quality of the hops on 
which they were applied. In order to test this point some nearly 
ripe hops were sprayed with the following materials, and when the 
crop was being picked these sprayed hops were picked, dried in the 
kiln with the other hops, and later sent to Washington for analysis: 

Nicotine sulphate, 1-1,000; whale-oil soap, 4 pounds to 100 gallons. 
Nicotine sulphate, 1-2,000; whale-oil soap, 8 pounds to 150 gallons. 
Nicotine sulphate, 1-3,000; whale-oil soap, 4 pounds to 100 gallons. 
Blackleaf tobacco extract, 1-00 and 1-75. each with 2 pounds of whale-oil soap to 
100 gallons. 
Quassia chips, 7^ pounds; whale-oil soap, 9 pounds to 250 gallons. 

The following analyses were received from the Bureau of Chemistry: 

Table VIII. — Analyses of hops sprayed with various insecticides. 



No. 


Whale-oil 
soap. 


Nicotine. 


3 

4 

5 

6 


None. 
None. 
None. 
None. 
None. 
None. 


None. 
None. 
None. 
None. 
None. 
None. 



The quassia was not tested for, as there is no test that is applicable. 

From the above analyses it is evident that the nicotine or whale-oil 
soap that remained upon the hop cones was not present in sufficient 
quantities to be detected by a chemical analysis, and therefore would 
not injure the quality of the hops. 

The flour paste is composed of starch and gluten, which has no 
distinct flavor or odor, and even through it were present in large 
amounts it can not be conceived how this material could influence 
the quality of the hops. 

DIRECTION IN WHICH TO WORK. 

Since the winged aphides travel largely with the wind, the best 
results will be obtained, especially where the winds are prevailingly 
from one direction, by working with the wind. If this is done the 



CONTROL OF THE EOP AIM! IS. 



31 



winged aphides will not be able to migrate to the sprayed hops so 
readily as if the wind were blowing from the unsprayed hop vines to 
those which have been sprayed. 

CONTROL ON PRUNE. 

The hop aphis apparently is capable of migrating some distance, 
provided the wind is right, and in prune-growing sections it is impos- 
sible to kill all of the migratory insects. Where there are only a 
few prime or plum trees in the neighborhood, however, the destruc- 
tion of any nonproductive trees and any wild plums that may be 
present will reduce the number of trees that will have to be sprayed. 

The spraying of the plums and prunes can not be relied upon for 
the control of the hop aphis, but where it is thoroughly and systemat- 
ically done the severity of the season's infestation may be greatly 
lessened. Work along this line is strongly recommended. 

FIELD OBSERVATIONS. 

About the time that the aphides are expected to appear upon the 
plum or hop it is advisable to go through the prune orchards or hop- 
yards and note the conditions. Careful observations, if maintained 
throughout the season, will keep the grower informed as to the 
severity of the infestation in all parts of his hopyards. He will then 
be able to check the infestation before any serious damage has been 
done. 

SPRAYING REPORT. 

The following form of a daily report was successfully used by Mr. 
H. N. Ord at Independence, Oreg., in 1912, to keep a record of the 
spraying operations in the field: 



Date. 


No. acres 
infested. 


No. acres 
sprayed. 


No. gallons 
used. 


Formula 
and cost 
per 100 
gallons. 


Effective- 
ness of 

spray ap- 
plied three 
days before. 


No. 

machines 

used. 


No. acres 
sprayed per 
machine. 


Cost of 
operations 
per acre. 


























































































































If such a report is faithfully kept the grower will always know the 
condition of his hopyard and what his spraying operations are costing 
him. 

SPRAYING MACHINERY. 

Several forms of outfits may be successfully employed in the hop- 
yards provided that they meet the following requirements: The 
machine should have a tank capacity of from 75 to 200 gallons, 



32 THE HOP APHIS IN THE PACIFIC REGION. 

should supply at least, two lines of hose at 120 to 150 pounds pressure, 
and should be in such order that there will be few breakdowns or 
delays. Good work can he done with the hand pumps (see PI. VII, 
fig. 1), the gasoline power outfits (PI. VIII, figs. 1,2), the compressed- 
air sprayers, etc, provided they meet these requirements and are 
supplemented by an efficient mixing and supply system. 

The knapsack spraying machine (PI. VII, fig. 2) may, under some 
circumstances, he of value for work on a very small scale, but is not 
at all practical in a commercial hopyard. 

BOILING AND MIXING PLANT. 

In designing a boiling and mixing plant for work on a large scale it 
is very desirable to arrange the tanks so that their filling and empty- 
ing is accomplished by gravity. 

The uppermost tanks should be used for steeping the materials and 
should be supplied with water from a hydrant; the lower ones 
should be tilled by drawing from the upper ones, or, when diluting is 
necessary, from a hydrant. The lower tanks, however, should be 
high enough to drain into a supply wagon. 

DESCRIPTION OP TANKS. 

The boiling and mixing tanks at Independence, Oreg., were made 
of No. IS galvanized iron, riveted and soldered together, a f-inch 
iron pipe forming a brace for the tops. Three braces of J-inch angle 
iron, placed 3 feet 4 inches apart and riveted to the sides of the tanks, 
together with a framework of 2 by 4 planks, prevented the tanks 
from bulging. 

ARRANGEMENT OK TANKS. 

The arrangement of tanks shown in Plate VI, figure 2, was found 
very satisfactory. Two boiling tanks 10 by 3 by 3 feet 9 inches, 
heated by steam, were placed upon a 10 by 12 platform, elevated 10 
feet from the ground. Passageways were left between and around 
the 1 tanks. On a near-by but lower platform were three 375-gallon 
tanks for mixing and storage. A swinging outlet pipe drained the 
boiling tanks and directed the materials into any one of the three 
tanks. From the lower tanks the material was run through a long 
hose into the supply wagons. In order thoroughly to strain the 
materials the entrances of all the outlet pipes were screened with 
wire gauze and the ends of the hose were covered with cheesecloth. 

FIELD OPERATIONS. 

SUPPLY WAGONS. 

When extensive spraying operations are being carried on it is 
essential to have an adequate supply system. In an emergency a 
farm wagon containing barrels of spray (PI. VIII, fig. 2) can be used, 



lureau of Entomology, U. S. Dept. of Agricultu 



Plate VII. 




Fig. 1.— Hand Pump and Barrel on Sledge. (Original.) 



■ *"**$* ^ 



*• WmMM 







Fig. 2.— Knapsack Spraying Machine in Use in Hopyard. (Original.) 
SPRAYING AGAINST THE HOP APHIS. 



Plate VII 




Fig. 1.— Power Outfit on Narrow Truck, in Use in Hopyard. (Original. 




Fig. 2.— Filling Power Outfit from Improvised Supply Wagon. (Original.) 
SPRAYING AGAINST THE HOP APHIS. 



Sureau of Entomology, U. S. Dept. of Agricultun 



Plate IX. 




Fig. 1.— Compressed-Air Spraying Machine, Showing Air Bottle, Tank, Reducing 
Valve, and Pressure Gauge. (Original.) 




Fig. 2.— Filling Air Bottles for Compressed-Air Spraying Machine. (Original.) 
SPRAYING AGAINST THE HOP APHIS. 



CONTROL OF THE HOP APHIS. 33 

but it is very desirable to have a large tank wagon made expressly 
for this purpose. When low spray tanks are used the spray can be 
run from the supply tank by gravity, but in most cases it is necessary 
to employ a good pump. 

EXCHANGE TANKS. 

When conducting spraying operations it is desirable to keep the 
entire force constantly employed. The use of an exchange tank is 
one of the best methods for accomplishing this purpose. An extra 
machine is filled after the other machines have started and is 
exchanged for the first one emptied. The exchange tank is driven 
down the row in which the nearly empty tank is working. When 
empty the men move back and take the exchange tank, the empty 
tank being then refilled and exchanged for the next empty tank. 

SPRAY RODS. 

When the hops are growing upon short poles the spray is most 
readily applied with a short spray rod. In the trellised yards, how- 
ever, the hops are much taller and a 10-foot rod is necessary. The 
aphides are mostly upon the underside of the leaves, and in order to 
wash them thoroughly the spray must be directed from below. 
When angle nozzles are not available the spray rod may be bent so 
that the spray is readily directed to the underside of the leaves. If 
one or the other of these methods is not employed the material will 
not be satisfactorily applied. 



By exercising great care it was found possible to spray the hop- 
vines thoroughly with a nozzle that produced a very fine mist spray. 
It was found much easier, however, to do the same work with a nozzle 
that produced a slightly coarser washing or driving spray. This 
type of spray is more satisfactory because by its driving force it 
turns the foliage and dashes over it. When cheap labor is employed 
good work is more readily obtained with the coarse driving spray 
than with the very fine mist spray. 

THE COMPRESSED-AIR SPRAYING MACHINE. 

The compressed-air spraying machine (PI. IX, fig. 1), which is 
described below, was invented by Mr. Theodor Eder, of Perkins, Cal., 
who by the following statement has generously dedicated it to the 
use of the public.' 

Whereas, I, Theodor Eder, of the town of Perkins, county of Sacramento, and 
State of California, having invented certain improvements in spraying devices for 

1 A copy of this patent (No. 1040572) may be obtained for 5 cents by addressing the Commissioner of 
Patents, Washington, D. C 



34 THE HOP APHIS IN THE PACIFIC REGION. 

which I filed on the 20th day of March, 1909, an application for patent of the United 
States, serial No. 484784; and 

Whereas, it is my desire that the public generally shall have the right to use said 
invention, 

Now, therefore, I, the said Theodor Eder, hereby dedicate, grant and convey to the 
public at large and to whomsoever may desire to use said invention, the full right, 
liberty and license to make, use and sell apparatus embodying the said invention for 
the full end of the term of any letters patent which may be granted on said application. 

And I hereby authorize and request the Commissioner of Patents to issue any letters 
patent which may be granted on said application to the people of the United .Stairs 
and Territories thereof as the assignee of my entire right, title, and interests in and to 
the same . 

In witness whereof, I have hereunto set my hand and seal this 31st day of October, 
A. D. 1912. 

Theo. Eder. 

This spraying machine (PI. IX, fig. 1) is composed of a large iron 
tank, fitted with a pressure gauge (/), an inlet pipe with a strong 
screw cap {2) which is opened with a large wrench (3), an outlet pipe 
with cut-off (4) and connected through a pressure-reducing valve (5) 
with a large air bottle (6). (A large carbonic-acid gas bottle serves 
this purpose, the larger the better.) This machine is fastened onto 
a truck made from two old mower wheels and an iron shoe. 

Provided that the spray material is thoroughly screened so that 
no dirt gets in to clog the nozzles, this machine is effective and is so 
small and light that it is readily hauled through a hopyard by one 
horse. 

The air bottles are filled with air compressed by the air compress 
to 1 ,000 of 1 ,200 pounds (PI. IX, fig. 2), loaded onto the supply wagon, 
-and hauled with the spray to the field. The spray tank is filled, an 
air bottle connected with the reducing valve which has been set for 
120 or more pounds pressure, the air is turned on, the pressure gauge 
indicates the pressure that is maintained, and the machine is ready 
for work. 

The following information was received from Mr. Eder and gives 
data from which the cost of such a machine may be estimated : 

Replying to your request in this regard , we beg to advise that the cost of these rigs 
depends upon the size of the spray tank, etc. A 150-gallon tank in black iron would 
cost about $42. The reducing valves which we use between the air bottles and the 
tank cost $10, including pressure gauges and fittings. Mowing machine wheels we 
buy old, costing from $1 to $1.50 per pah. The axles and other iron work on the truck 
cost in the neighborhood of $8, and the woodwork, etc., would probably bring the 
entire truck construction up to $15. The only things you would now have to add are 
spray hose, pipe, and nozzles, which expense would, of course, vary according to the 
number of leads and the length of same. We usually use four leads, two of 16 feet and 
two of 25 feet. We use seven-ply £-inch hose, costing about 12 cents per foot, and use 
10 feet of J-inch pipe for spray rod to each lead, and a hop nozzle, which costs approxi- 
mately 90 cents. The value of the pipe and valve would probably be $1. The air 
bottles, if purchased in lots, cost $12; singly, probably $15. 

For further information we beg to advise that a crew of four spray hands will empty 
a 250-gallon spray tank on hops about five to six times a day, and this would require 



(ONI KOI. OF Til K HOP APHIS. 35 

one full air bottle to each tank of spray. However, the same bottles are charged 
several times in a day, and on some ranches we run 10 or 12 spray rigs with three dozen 
but lies, and could probably get along with a few bottles less, if necessary. 

The air compressor we use is a 10 by 12 double-acting mine compressor with the 
valves removed from one end. The piston rod is continued on through and the initial 
compressor puts the air through pipes immersed in water that cool same, and the ramat 
the oilier end of the piston rod puts this air up to 1,000 pounds. We use XX f-inch 
sleel pipe for leads, and usually fill three or four bottles at a time, or new bottles can 
be pul on and others taken off, without stopping the compressor. The compressor we 
have designed will charge about 25 bottles per hour, if necessary, all from 1,000 to 1,200 
pounds. Lately we are charging quite a lot at 1,200 pounds, especially where we use 
250-gallon tanks. Cost of compressor, as fitted, $550. 

K< tr small growers it would seem to us that they could club together and buy a com- 
pressor and bring their empty air bottles in for recharging, as a bottle gets away with a 
lot of spray even at high pressure. The reducing valves are so constructed that any 
pressure desired is obtained . We have also tried the use of carbonic-acid gas for spray- 
ing, but we use the spray material up so fast that the gas freezes itself up in the valve 
while coming out of the bottle when the pressure is being reduced. This could be 
overcome by the use of an alcohol lamp in the lead line, but this is too cumbersome; 
besides, air costs less. 

E. Clemens Horst Co., 
By Theo. Eder. 

COST OF SPRAYING. 

The following estimate of the cost of spraying for the hop aphis is 
made from data taken from actual field work on high- trellis yards. 
The amount of material needed for hops on short poles will be some- 
what less. 

It has been found that one machine will spray from 2 to 3 acres 
per day, and that in order to do thorough work it is necessary to 
apply from 300 to 500 gallons per acre according to the amount of 
foliage on the vines. The following data are based upon a machine 
which will spray 2 acres per day: 

Materials: Nicotine sulphate, 1-2,000; flour paste, 4-100. Cost, 70.8 cents per 100 
gallons. 

300 galls. 500 galls. 

Applying per acre $2.13 $3. 54 

Labor, 3 men, $2 per day fori day 3.00 3.00 

1 horse, 50 cents per day for .1 day 25 .25 

Total cost per acre of I application 5. 38 0. 79 

Quassia and Whale-Oil Soap. — Formula No. 2. 

( !os1 of materials per LOO gallons $0. 09 

Cost of cooking 11 

To! al 80 

300 galLs. 500 galls. 

Applying per acre $2.-10 $4. 00 

I. a hoi, 3 men, $2 per day for J day 3.00 3.00 

I horse, 50 cents per day for J day 25 .25 

Total cost of I application 5. 05 7. 25 



36 



THE HOP APHIS IN THE PACIFIC REGION. 



The cost of stripping the vines preliminary to spraying will be from 
$1.80 to $2 per acre. 

The cost of spraying for the hop aphis, although apparently great, 
is nothing compared to the losses which result from neglect to spray 
for this insect. 

Thorough spraying is, then, a good business policy and should be 
carefully done by all commercial hop growers. 

CULTURAL METHODS. 
CLEAN CULTURE. 

Suckers growing between the rows and vines growing over fences 
and near-by trees usually have much dense foliage, due to the growth 




'-'9k 







Fig. 8.— Short-pole hopyard, showing dense foliage around base of vines, which harbors the hop aphis. 

(Original.) 

of several plants upon a limited area, and form an ideal breeding place 
for the aphides. Such plants may form a constant source of infesta- 
tion and should be promptly removed. 

STRIPPING THE VINES. 

One of the most important cultural methods now in use is stripping 
the vines to a point about 4 feet above the ground (fig. 8). This 
removes the suckers and dense foliage, which protect and foster the 
aphides, from around the base of the vines. Experiments show that 



Sureau of Entomology, U. S. Dept. of Agricultu 







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GENERAL SUMMARY, WITH RECOMMENDATIONS. 37 

when the vinos are stripped and tied together above the point of 
stripping (PL X, fig. 2) the foliage below this point is matted and 
difficull to spray thoroughly, but that when the vines are tied below 
the first foliage (PL X, fig. 1) the loaves are free and the undersides 
are readily treated. Stripping the vines is a necessary preliminary 
to the successful control of the hop aphis and should be done before 
commencing to spray. 

PICKING OFF INFESTED LEAVES. 

It is the custom of some growers to pick off the infested leaves and 
throw them on the ground. This practice reduces the infestation 
somewhat, but even though all of the removed aphides die, there are 
many scattered ones left upon the vines which will soon cause 
reinfestation. The writer has never observed any good results from 
this practice alone. 

FERTILIZATION AND IRRIGATION. 

Stimulation of the vines helps them to resist the draining effect of 
the aphides and encourages the production of the hops, but does not 
retard the insects in the least, the resulting dense foliage favoring 
their development. Proper irrigation and fertilization invigorate 
the hopvines and are very beneficial, but when an infestation occurs 
they should be supplemented by thorough spraying operations. 

GENERAL SUMMARY, WITH RECOMMENDATIONS. 

The investigation of the life history and control of the hop aphis 
has brought out the following points: 

(1) The hop aphis, if not carefully controlled, always injures and 
may cause a total loss of a large portion of the crop. 

(2) The insect may hibernate upon the plum or the hop. The 
destruction of the hibernating forms will aid in the control of this 
insect. 

(3) The insect is readily killed by several contact insecticides. 

(4) Several applications may be necessary to control an infestation 
successfully. 

(.*>) If successful control is desired the spraying operations must not 
h, (hbnjid and the work must be very thorough; all of the loaves of 
the vines must be wetted on both sides. It is more economical to 
waste a little material than not to apply enough. 

(6) Severe infestations have been successfully checked and clean 
hops obtained where the spraying operations were thorough. 



38 THE HOP APHIS IN THE PACIFIC REGION. 

THE MORE IMPORTANT WRITINGS ON THE HOP APHIS. 

1904. Clarke, W. T.— Bui. 160, Univ. Cal. Agr. Exp. Sta., 13 pp., 7 figs. 
1897. Cordley, A. B.— Bui. 45, Oreg. Agr. Exp. Sta., pp. 99, 127, 13 figs., June. 
Habits and remedies. 

1903. Felt, E. P.— Proc. 24th Ann. Meet. Soc. Prom. Agr. Sci., pp. 39-48. 
1865. Fitch, A.— The Country Gentleman, vol. 25, p. 274. April 27. 

Destructiveness, enemies, and remedies. 

1904. Fletcher, J.— Bui. 46, Div. Ent,, U. S. Dept. Agr., pp. 82-88, May. 
1904. Fletcher, .1. — Rept. Exp. Farms Canada, pp. 163-215. 

1887. Howard, L. O. — Country Gentleman, vol. 52, p. 875, November 17. 
First published full life history. 

1897. Howard, L. O.— Bui. 7, n. s., Div. Ent,, U. S. Dept. Agr., pp. 84-87. 

1899. Howard, L. O.— Hop Industry, Orange Judd Co., New York, pp. 113-141, 19 

figs. 
Accounts of the species known to affect hops. 
1893. Koebele, A. — Insect Life, vol. 6, pp. 12-17, November. 
Experiments with hop louse in Oregon and Washington. 

1887. Lintner, J. A.— Cultivator and Country Gentleman, vol. 52, p. 511, June 30. 
Remedies. 

1889. Lintner, J. A.— New England Homestead, p. 253, July 27. 
Remedies for hop aphis. 

1891. Lintner, J. A. — New England Homestead, p. 193, May 2. 

How to control the hop aphis. 

1900. Lugger, O.— Bui. 69, Minn. Agr. Exp. Sta., pp. 250, 200 figs., 16 pis. 
1904. Pettit, R. H.— Spec Bui. 24, Mich. Agr. Exp. Sta., pp. 79, 70 figs. 

1908. Remisch, Fr.— Zeitschrift fur wissenshaftliche Insektenbiologie, vol. 4, no. 10, 
pp. 365-366. 

Important enemy of hops. 

1910. Remisch, Fr.— Zeitschrift fur wissenshaftliche Insektenbiologie, vol. 6. no. 6, 

p. 242. 
Mentioned in article on Adalia bipuncta/a as the principal food of that species. 

1911. Remisch, Fr. — Zeitschrift fur wissenschaftliche Insektenbiologie, vol. 7, nos. 

7-8, pp. 240-243; no. 9, pp. 282-285. 
Article, "The hop leaf louse, Aphis humuli." 
1891. Riley, C. V.— Cir. 2. 2d ser., Div. Ent., U. S. Dept. Agr., pp. 7, 5 figs., 1 pi., 

June. 
1891. Riley, C. V.— Insect Life, vol. 3, pp. 181-210, January. 
1893. Riley, C. V.— Ann. Rept, U. S. Dept. Agr., pp. 199-226. 3 pis. 
1891. Riley, C. V., and Howard, L. 0.— Insect Life, vol. 3, p. 350, April. 
1891. Riley, C. V., and Howard, L. ().— Insect Life, vol. 3, p. 486, August. 
Hop lice on Pacific Coast. 

1891. Riley, C. V., and Howard, L. O.— Insect Life, vol. 4, p. 84. October. 

Quassia for the hop aphis. 

1892. Riley, C. V., and Howard, L. O.— Insect Life, vol. 4, pp. 342-343, June. 

Hop louse in the extreme northwest, 

1892. Riley, C. V., and Howard, L. O.— Insect Life, vol. 4, p. 401, August. 

Hop aphis remedies. 
1892. Riley, C. V., and Howard, L. O.— Insect Life, vol. 4, p. 406, August, 

The hop louse in Oregon. 

1892. Riley, C. V., and Howard, L. O— Insect Life, vol. 5, p. 60, September. 

The hop plant-louse in Washington. 

1893. Riley, C. V., and Howard, L. O.— Insect Life, vol. 6, p. 53, November. 

Hop lice in New York State. 



MORE IMPORTANT WHITINGS ON HOP APHIS. 39 

1912. Sanderson, E. D.— Insect Pests of Farm, Garden, and Orchard, pp. 275-278, 
rigs. 202-204. 
On hop. 

1891. Washburn, F. L.— Bui. 10, Oreg. Agr. Exp. Sta., pp. 23-24, figs. 5. 

Description and treatment. 

L893. Washburn, F. L. — Bui. 25, Oreg. Agr. Exp. Sta., pp. 9-12. 

Treatment. 

1894. Washburn, F. L.— Bui. 31, Oreg. Agr. Exp. Sta., pp. 79-88, 3 figs., 2 pis., 

April. 
1894. Washburn, F. L.~ Bui. 31, Oreg. Agr. Exp. Sta., p. 82, April. 
Brief notes, with suggestions as to remedies. 



INDEX. 



Page. 

Adalia bipunctata, enemy of hop aphis 23 

Anthocoris sp., enemy of hop aphis 23 

Ants, relation to hop aphis 19 

Aphides on shrubs and trees near hopyards mistaken for hop aphis 21 

Aphis, hop, bibliography of more important writings 38-39 

control axioms 23 

measures 23-37 

on prune 31 

recommendations, summary 37 

damage, nature 21-22 

deposition of young 14-15 

early history 9 

economic importance 9-10 

effect, general, upon hops 21-22 

of heat thereon 20-21 

eggs, winter 17-18 

emergence from hibernation 12 

enemies, natural 22-23 

favorable and unfavorable conditions therefor 20-21 

field observations, importance in control work 31 

operations in control 32-35 

first appearance in season 20 

food plants 21 

generations, number on host 13 

growth, rate 15-16 

habitation 19 

habits 19-20 

head compared with that of melon aphis 15 

hibernation 10 

emergence therefrom 12 

insecticides used in control 23 

life history 10-19 

losses due to its work 10 

migrants, fall 17 

summer, theory regarding them 18-19 

migratory activities 13-14 

migrating forms 13 

necessity for thorough work in control 24 

number of spray applications used in control 24 

young deposited by viviparous females 16-17 

on hop roots 10-12 

procrastination in control work, results 24 

protection 19 

relation of ants thereto 19 

41 



42 THE HOP APHIS IN THE PACIFIC REGION. 

Page. 

Aphis, hop, reproduction, method 12-13 

spraying experiments in control 24-27 

time to begin 23-24 

nummary, general 37 

young, number deposited by viviparous females 16-17 

melon, comparison of head with that of hop aphis 15 

Aphis gossypii. (See Aphis, melon.) 

Boiling and mixing plant for spraying against hop aphis 32 

Camptobrochis nebulosus, enemy of hop aphis 23 

Chilocorus orbus, enemy of hop aphis 22 

Chrysopa californica, enemy of hop aphis 22 

Cladosporium sp., blackening of hops caused thereby 22 

growing on honeydew excreted by hop aphides 2 ! 22 

Clean culture against hop aphis 36 

Coccinella abdominalis, enemy of hop aphis 22 

californica, enemy of hop aphis 22 

Compressed-air spraying machine, use against hop aphis, description 33-35 

Cost of spraying against hop aphis 35-36 

Cultural methods against hop aphis 36-37 

I >irection in which to work in spraying against hop aphis 30-31 

Fertilization in control of hop aphis 37 

Flour paste, advantages over whale-oil soap as a spreader for contact insecti- 
cides 28 

and nicotine sulphate against hop aphis 26-27 

cost per 100 gallons 35 

effect on quality of hops 30 

preparation 27 

Formica subsericea, relation to hop aphis 19 

Fungus, smut. (See Cladosporium sp.) 

Heat, effect on hop aphis 20-21 

Hippodamia convergens, enemy of hop aphis 22 

Honeydew excreted by hop aphis, black-smut. fungus (Cladosporium sp.) grow- 
ing thereon 21 

effect on hops 22 

Hop aphis. (See Aphis, hop.) 

food plant of hop.aphis 21 

picking off infested leaves for control of hop aphis 37 

sometimes winter host plant of hop aphis 14 

vines, damage by black-smut fungus (Cladosporium sp.) growing on honey- 
dew excreted by hop aphis 21-22 

stripping them in control of hop aphis 37 

Hops, blackening caused by smut fungus, Cladosporium sp 22 

quality as affected by spray materials used against hop aphis 30 

Irrigation in control of hop aphis 37 

Lime sulphate ineffective against hop aphis 25 

Machinery for spraying against hop aphis 31-35 

Nicotine solutions, mixing them with whale-oil soap 27 

sulphate against hop aphis 25-27 

and cresol soap against hop aphis 25 

flour paste against hop.aphis 26-27 

cost per 100 gallons 35 

Lye-resin soap against hop aphis 25 

whale-oil soap against hop aphis 25-27 



INDEX. 43 

' Page. 

Nozzles for spraying against hop aphis 33 

Phorodon humuli. (See Aphis, hop.) 

Picking off infested loaves as remedy against hop aphis 37 

Picra na excelsa. (See Quassia.) 

Plum, winter hosl plant of hop aphis 14 

Prune, winter host plant of hop aphis 14 

Quassia against hop aphis 28-30 

and whale-oil soap, cost per 100 gallons 35 

effective only by contact 30 

effect on aphides 28 

formulas 29 

noninjurious to hops 30 

preparation 29 

quality 29 

Report form for use in spraying against hop aphis 31 

Rods for spraying against hop aphis 33 

Sloe, winter host plant of hop aphis 14 

Soap, cresol, and nicotine sulphate against hop aphis 25 

ineffective against hop aphis 25 

lye-resin, and nicotine sulphate against hop aphis 25 

ineffective against hop aphis 25 

whale-oil, and nicotine sulphate against hop aphis 25-27 

quassia, cost per 100 gallons 35 

mixing it with nicotine solutions 27 

versus flour paste as a spreader for contact insecticides 28 

Spraying against hop aphis, boiling and mixing plant, « 32 

cost 35-36 

direction in which to work 30-31 

exchange tanks 33 

nozzles 33 

spraying machinery 31-35 

report in daily use 31 

spray rods 33 

supply wagons 32-33 

tanks, arrangement 32 

description 32 

. exchange 33 

Spraying machine, compressed-air, description and patent by Theo. Eder 33-35 

Spray materials against hop aphis, effect on quality of hops 30 

Stethorus punctum, enemy of hop aphis 23 

Supply wagons for spraying against hop aphis 32-33 

Syrphus inmricanus, enemy of hop aphis 22 

opinator, enemy of hop aphis 22 

Tanks, exchange, for spraying against hop aphis 33 

for spraying against hop aphis, arrangement, description 32 

Tobacco solution, blackleaf, against hop aphis 25 

waste solution against hop aphis 25-26 

Triphleps insidiosus, enemy of hop aphis 23 

Weather. (See Heat.) 

o 



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